Interesting photoluminescence behaviour in graphitic carbon nitride quantum dots attached to PbCrO4 colloidal nanostructures

Abstract

Highly luminescent graphitic carbon nitride quantum dots (CNQDs) are synthesized by a facile one-step hydrothermal route using urea and ethylenediamine as precursor materials. The as-synthesized CNQDs show excitation-dependent photoluminescence (PL) behaviour. We have successfully synthesized a CNQD–PbCrO₄ colloidal nanocomposite at room temperature and studied its photoluminescence properties. Here, Pb(II) ions do not shown any fluorescence quenching effect, but in the presence of Cr₂O₇²⁻ ions fluorescence quenching of the characteristic peak of CNQDs at 400 nm occurs and also a new peak appears at 542 nm due to the formation of a PbCrO₄ colloidal nanostructure. Pb²⁺ and Cr₂O₇²⁻ ions act as a unique ion pair for this experiment. The in situ formed PbCrO₄ nanostructure is characterized by HR-TEM and XRD, and zeta potential and photoluminescence measurements are also carried out. These CNQD materials selectively detect toxic yellow lead chromate pigment with high quenching efficiency and a low detection limit of 391 nM.